Posted by: rocknrev | November 6, 2009

Let There Be Light and Let it be the Correct Color

Lights come in many shapes and sizes, and emit various colors. The easiest way to understand how color works with lights is to picture in your mind a STANDARD incandescent light bulb. If you are picturing the correct light, it’s a little yellowish in color isn’t it? That light’s color is described by a “temperature” number, 2700K. It is not necessary to understand all the science behind the number. Just remember that any light regardless of size or shape will be the similar in color if it is rated as 2700K. The yellow color is a result of there being a high amount of red in the lights spectrum.

The popular COOL WHITE light bulb actually has a littler more blue in its spectrum, so it is sometimes referred to as BLUE WHITE and has a color number between 3500K to 4100K. This is probably the most common light color we use in the United States. I know there is one company that sells their regular light bulbs in yellow boxes while their cool white lights are sold in white boxes–an easy way to pick the correct bulb at the grocery or variety store.

Some people like even brighter lights that have a color rating of 5000K. If you are following the pattern developing here, you’ve already figured out that the higher the color number—the whiter and brighter the light! So-called “Daylight” bulbs are usually rated around 6500K and will strain most peoples eyes if looked at directly.

Warmer colors in the 2700K-3300K tend to have a relaxing effect while “cool” colors in the 4100K and above range are helpful in office situations and facilitate better concentration for the end-user. Of course, all these numbers and how we perceive them are somewhat arbitrary. The lighting industry uses a CRI rating (Color Rendering Index) which is a way to measure how a light will reproduce the colors of various objects accurately. A CRI rating of 100 would be considered more or less perfect and would reproduce colors very close to a natural light source like the sun. The higher the number then, the more accurate colors will appear. Artists and photographers would be a couple of examples of professionals that would want high CRI lighting for their work.

Unfortunately, the way various manufacturers design their code numbers is not universal. In most cases the color of the bulb will appear near the end of the light’s code stamped on the bulb or it’s metal base. To complicate things further, manufacturers tend to drop some or all of the zeros. So, you’ll sometimes see a number like “741” in the code and it’s the “41” that tips you off that it is a 4100K bulb. A code ending with 850 is really a bulb with the 5000K brightness. In most cases with a little practice, you’ll be able to see how the light color system works. The leading number “7” or “8” most often gives you a hint of the bulbs CRI rating. Again, the higher the number the truer that bulb will render colors.

You may find this information useful in your personal life when you go to the store to buy lights. Next time you go to the store, spend a few minutes looking at the codes. You’ll know better ahead of time just what color and how bright a light you are purchasing will be. If you have a burnt out bulb you want to replace, be sure to write the code number down so when you are shopping, you make sure the bulb you buy is the same color as the dead bulb back home.

It is OK to share and reproduce this information as long as you referance my blog.


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